Copper promoted coupling

Copper-promoted coupling of RflCH=CIRf2 compounds gives the 1,2,3,4-tetrakis(perfluoroalkyl)-l,3-butadienes m 62-77% yields [250 ... 

Nickel catalysed ethylzincation of diphenylethyne to give ( )-( 1,2-diphenyM-butenyDethylzinc and its conversion to ethyl ( )-2-methylene-4,5-diphenyl-4-heptenoate by copper promoted coupling with ethyl a-(bromomethyl)acrylate6Z... 

Since then, experiments have been reported which indicate that (1) organocopper compounds will couple with aryl halides (2) arylcopper compounds can be oxidatively and thermally dimerized (3) arylcopper compounds are intermediates in the Ullmann reaction (4) organocopper compounds are intermediates in copper-catalyzed decarboxylations and (5) copper-promoted coupling reactions are not restricted to aromatic halides. The copper(I) oxide-promoted coupling reactions, however, have still to yield firm evidence of a copper intermediate. 

The disconnections for copper promoted coupling of alkynes and alkenes are... 

Table 3.54 Copper-Promoted Coupling of Arylboronic Acid With Amines ...

As early as 1901, Ullmann discovered the copper promoted coupling of aryl halides to biaryls, one of the first uses of transition metals in synthesis. The mechanism is still not entirely clear, but a binuclear reductive elimination of Ar—Ar from CuAr is possible. 

The copper-promoted coupling of alcohols with vinyl boronates and boronic acids has been reported with yields as high as 99% [109]... 

The copper-promoted coupling of vinylboronic acids with amines and amides bearing reactive N-H groups has been achieved (Scheme 3.118) [125]. Using the combination of copper acetate and pyridine along with air as an oxidant, a number of enamines and enamides were prepared in moderate to excellent yield. One practical advantage to this chemistry was the observation that it could be carried out in air. 

The development of new approaches for the functionalization of nucleobases remains a current and challenging goal for the synthetic community. To this end, an efficient process for the N-vinylation of a variety of purine and pyrimidines has been devised using a copper-promoted coupling reaction (Scheme 3.119 and Example 3.18) [51]. A variety of... 

SCHEME 3.148 Copper-promoted coupling of terminal alkynes with secondary amides [165]. 

Bolm prepared a wide range of N-vinyl sulfoximine derivatives by means of copper-promoted coupling of A//-sulfoximines and vinyl bromides (Scheme 38) [126]. The major drawback of such protocol, which relied on the use of stoichiometric amounts of both copper and diamine ligands, was balanced by the fact that the present method exhibited broader scope than the one involving palladium-catalyst [73] being found compatible with the conversion of di-, tri-, and even tetra-substituted vinyl bromides. 

An approach to the preparation of asymmetrically 1,2-disubstituted 1,2-diamines has been reported the zinc-copper-promoted reductive coupling of two different N-(4-substituted)phenyl aromatic imines, one bearing a 4-methoxy and the other a 4-chloro substituent, in the presence of either boron trifluoride or methyltrichlorosilane, gave a mixture of the three possible 1,2-diamines, where the mixed one predominated [31 ]. Low degrees of asymmetric induction were observed using 1-phenylethylamine, phenylglycinol and its 0-methyl ether, and several a-amino acid esters as the chiral auxiharies meanwhile the homocoupling process was not avoided (M.Shimizu, personal communication). 

In a similar reaction, Knochel and co-workers synthesized allylpyrimidine 63 through a magnesium-iodine exchange with iodopyrimidine 62, followed by copper (I) promoted coupling with allylbromide . 

The results given above clearly demonstrate the good leaving group ability of the readily introduced benzylsulfanyl moiety in copper-promoted, Pd-catalyzed cross-coupling reactions. Moreover, the use of non-protected polyhydroxylated substrates has proven to be compatible with the cross-coupling conditions. 

Coupling of acetylenes and halides, copper-promoted, 50,100 Cuprous chloride, reaction with an organo-magnesium compound, 50,98... 

When vinyl silicon tnfluonde is treated with two equivalents of potassium fluonde, a new reagent, a dipotassium organopentafluorosilicate, is formed [101] This intermediate has found application as a component in an efficient stereoselective copper chlonde-promoted coupling reaction (equation 81)... 

Scheme 5. Copper(ll)-promoted coupling of boronic acids with phenols. R1 = 4-Me, 2-CI, 2-1, 2-OMe, 4-CH2CH(NHBoc)C02Me, 3,5-tBu2 R2 = 4-Me, 4-F, 4-OMe, 3-OMe, 3-N02, 2-Me, 2-OMe, 3-CI-4-F.

Scheme 6. Proposed mechanism for the copper(ll)-promoted coupling of boronic acids with phenols.

The reaction of 3-(chloromethyl)-A3-cephem 62 with organotins in the presence of copper(l) chloride, and the related copper(0)-promoted coupling reaction of 62 with allyl and benzyl bromides have been investigated <1997JOC3782>. It was found that both reactions could be achieved only in the presence of terpyridine (tpy) or bipyridine (bpy) as a ligand, to afford 3-alkyl-A3-cephems 63 and 3-(arylalkyl)-A3-cephems 64, respectively (Scheme 12). 

---